How long does my Thai wife need to stay in the UK to maintain her ILR status?

Ronnie Jasper Hey, I don't make the rules! It matters because if Immigration suspect that she only returns to reset her visa, they can revoke it. In such circumstances they may ask for proof of a genuine return. Until she obtains citizenship it doesn't matter that she is the spouse of a British citizen or not. When the original visa application was made, she will have signed to say that she intended to live in the UK permanently.

Joni1828 I will leave the above in place as you may have read it and then not read any edit. I think you can ignore the bit about visa start dates - that applies to pre - ILR. In your wife's case with ILR its 2 continuous years outside the UK. Her ILR is automatically cancelled after 2 years. Sorry for the confusion. I would remind you though about her being considered as abusing her ILR. I know this because my ex (with ILR) was questioned after several long stay trips back to Thailand. They didn't total 2 years and were not continuous but the officer told us that if he felt she was using ILR as a glorified tourist visa, he could revoke it.

Joni1828 Ok well the 'rules' state that she cannot be out of the UK for more than 2 years but as I say, if its suspected that she is actually living abroad, she may be questioned and if they are not satisfied - denied entry. I understand it rare but it can happen. Note also that the start date for calculating the 2 years is the start date printed on her visa - not the date she actually entered the UK. People have been caught out that way.

Joni1828 is it a single entry or multiple entry you have